Crystallite formation mechanism of CuIn(Se,S)2 synthesized using solvothermal method

This study developed a novel CuIn(S1-xSex)(2) (CISS) crystal solvothermal synthesis method with a short reaction time. The ethylenediamine aqueous solution concentration, reaction temperature and time effects on crystal phase development and morphology were investigated. A single CISS phase with a crystallite size of about 200 nm can be synthesized using the solvothermal process using 50 vol% ethylenediamine aqueous solution as the solvent and sodium thioglycolate (TGA) simultaneously as a chelating agent, a reducing agent and the sulfur source at 200 degrees C for 3 h. The CISS nanocrystals formation mechanism using the solvothermal process can be divided into the following steps. The first step is Cu2-xSe phase formation at low reaction temperatures for short periods of time. Amorphous In-x(S,Se)(y) was formed as the reaction time was prolonged or the reaction temperature was raised. Cu2-xSe crystallites were then gradually dissolved into the solution by ethylenediamine. Copper ions then displaced indium ions by cation exchange reaction in amorphous In-x(S,Se)(y) particles, or occupied the vacant sites of indium ions to form CuIn(Se,S)(2) crystals. (C) 2014 Elsevier Ltd and Techna Group S.r.l. All rights reserved.